atrium

(noun)

an upper chamber of the heart that receives blood from the veins and forces it into a ventricle

Related Terms

Examples of atrium in the following topics:

  • Structures of the Heart

    • There are one atrium and one ventricle on the right side and one atrium and one ventricle on the left side.
    • In addition, the right atrium receives blood from the coronary sinus, which drains deoxygenated blood from the heart itself.
    • The left atrium then receives the oxygen-rich blood from the lungs via the pulmonary veins.
    • Blood is pumped from veins of the systemic circuit into the right atrium of the heart, then into the right ventricle.
    • From the pulmonary circuit, blood re-enters the heart through the left atrium.

  • Types of Circulatory Systems in Animals

    • Fish have a single circuit for blood flow and a two-chambered heart that has only a single atrium and a single ventricle (figure a).
    • The atrium collects blood that has returned from the body, while the ventricle pumps the blood to the gills where gas exchange occurs and the blood is re-oxygenated; this is called gill circulation.
    • The blood then continues through the rest of the body before arriving back at the atrium; this is called systemic circulation.

  • The Cardiac Cycle

    • The internal pacemaker starts at the sinoatrial (SA) node, which is located near the wall of the right atrium.
    • The pulse reaches a second node, the atrioventricular (AV) node, between the right atrium and right ventricle, where it pauses for approximately 0.1 seconds before spreading to the walls of the ventricles.

  • Other Hormonal Controls for Osmoregulation

    • It is released by cells in the atrium of the heart in response to high blood pressure and in patients with sleep apnea.

  • Chordates and the Evolution of Vertebrates

    • The filtered water then collects in the atrium and exits through the atriopore.

  • Characteristics of Mammals

    • Mammals also have a specialized group of cardiac fibers located in the walls of their right atrium called the sinoatrial node, or pacemaker, which determines the rate at which the heart beats.

  • Mammalian Systems and Protective Mechanisms

    • Air flows into the atrium of the alveolar sac, then circulates into alveoli where gas exchange occurs with the capillaries.